Messages in this thread Patch in this message | | | Date | Sat, 11 Apr 2009 20:45:46 +0100 | From | Luis Henriques <> | Subject | Re: Problem with kvm on -tip |
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Hi,
On Sat, Apr 11, 2009 at 03:08:55PM +0300, Avi Kivity wrote: > > This might be fixed by the attached patch.
I confirm that the patch you sent removes the warnings but does it really solve the issue? (Sorry, I really do not know this code so I might be saying something really stupid.)
What I understand from your patch is that the only portion of code that needs protection is the __get_cpu_var(). If this is true then a patch like the one below would do a better job. But I am not sure that nothing else needs protection since the code immediately following the preempt_enable (in your patch) is an invocation to local_irq_save()...
--- arch/x86/kvm/x86.c | 10 +++++++--- 1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8ca100a..cf918b5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -626,13 +626,17 @@ static void kvm_write_guest_time(struct kvm_vcpu *v) unsigned long flags; struct kvm_vcpu_arch *vcpu = &v->arch; void *shared_kaddr; + uint32_t tsc_khz; if ((!vcpu->time_page)) return; - if (unlikely(vcpu->hv_clock_tsc_khz != __get_cpu_var(cpu_tsc_khz))) { - kvm_set_time_scale(__get_cpu_var(cpu_tsc_khz), &vcpu->hv_clock); - vcpu->hv_clock_tsc_khz = __get_cpu_var(cpu_tsc_khz); + preempt_disable(); + tsc_khz = __get_cpu_var(cpu_tsc_khz); + preempt_enable(); + if (unlikely(vcpu->hv_clock_tsc_khz != tsc_khz)) { + kvm_set_time_scale(tsc_khz, &vcpu->hv_clock); + vcpu->hv_clock_tsc_khz = tsc_khz; }
/* Keep irq disabled to prevent changes to the clock */ -- 1.6.2.1
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